Abstract: An interspecific antigen of Mycobacteria consists essentially of a mixture in substantially immunochemically pure form of a protein having a molecular weight of at least about 4.times.10.sup.6 Daltons and polysaccharide having a molecular weight of at least about 1.times.10.sup.6 Daltons, and has when subjected to cross-electrophoresis an immunoelectrophoretic precipitation pattern corresponding to A60-antigen of Mycobacteria bovis strain BCG. This antigen is effective for detecting the prior exposure of a subject to Mycobacterial infections by a cutaneous test.

Abstract: The sensitivity of hemagglutination inhibition tests is improved by introducing a determined amount of lyophilized antigen or antibody into serological tubes in the absence of the indicator component. The test fluid to be analyzed is incubated solely in the presence of its binding partner in a liquid phase. After completion of the binding reaction (about 5 hours but extendable to 18 hours), the sensitized indicator solid phase, usually consisting of sensitized red blood cells, is added. By this process a 10 to 20 fold increase in sensitivity of the hemagglutination inhibition test is routinely achieved.